Process of differentially crimping

ABSTRACT

Drawable filaments of polyesters, polyamides or polyolefines are crimped by applying a modifying process differentially across the filaments cross-section, including differential heating, while the filaments pass between the nip of two nip rollers, simultaneously with drawing the filaments by drawing means operating upstream and/or downstream of the nip so that the draw point is at or close to the nip. Further features comprise feeding the filaments to and from the nip along the common tangent to the two nip rollers and drawing the filaments by equal amounts upstream and downstream of the nip, to give a total draw which equals the maximum natural draw which can be attained. Alternatively the filaments can be laid with an arc of pre-wrap or post-wrap on one or other of the nip rollers, which preferably are differentially heated.

United States Patent [1 1 [111 3,803,675 Waterhouse Apr. 16, 1974 PROCESS OF DIFFERENTIALLY CRIMPING Primary Examiner-Louis K. Rimrodt [75] Inventor: George Waterhouse, Macclesfield, Attorney Agent or Flrm Mlchael Smker England [73] Assignee: Ernest Scragg & Sons Limited, [57] ABSTRACT Macclesfield, England Drawable filaments of polyesters, polyamides or polyolefines are crimped by applying a modifying process [22] Flled' 1971 differentially across the filaments cross-section, in- [21] Appl. No.: 208,829 cludin difierential heating, while the filaments pass g between the nip of two nip rollers, simultaneously with drawing the filaments by drawing means operating up- [30] Foreign Apphcatlon F Data stream and/or downstream of the nip so that the draw Dec. 17, 1970 Great Britain 59873/70 point is at or close to the Further features prise feeding the filaments to and from the nip along [52] U.S. Cl. 28/72.l the common tangent to the two nip rollers and draw hit. Cl. g the filaments equal amounts upstream and Fle'd of Search 72.1, downstream f the p to g a total draw which 264/168 equals the maximum natural draw which can be attained. Alternatively the filaments can be laid with an [56] References C'ted arc of pre-wrap or post-wrap on one or other of the UNIT D TA PATENTS nip rollers, which preferably are differentially heated. 3,358,345 12/1967 Daniel 28/12 3,374,302 3/1968 Stanley 264/168 14 Clams 1 Drawmg F'gme PROCESS OF DIFFERENTIALLY CRIMPING -This invention relates to crimping filaments, for example filament yarns of polyesters or polyamides or polyolefines.

The invention comprises a method of crimping drawable filaments comprising the step of applying a modifying process or processes differentially across the filament cross-section while passing the filaments through the nip of two rollers and drawing the filaments so that the draw point or region of necking is at or close to the nip. The drawing may be effected by drawing means operating upstream and/or downstream of the nip.

The differentially applied modifying process may include differential heating so that there is a temperature gradient across the cross-section of the filaments while passing through the nip. The filaments may be subjected to a predetermined pressure at the nip of the two rollers, and the pressure may be adjustable.

' The filaments may enter and leave the nip tangentially of the two rollers.

One roller may be a hot roller and the other a cooler roller and the filaments approaching the nip maybe laid upon the hot roller with a short are of pre-wrap in advance of the nip, and/or the filaments leaving the nip may be laid upon the hot roller with a short are of postwrap after the nip. When drawing means operating both upstream and downstream of the nip are employed, the total draw imparted to the filaments may be effected in substantially equal proportions by the two drawing means, and the total draw imparted may be equal to the maximum natural draw achievable having regard to the material from which the filaments are made.

The invention also comprises apparatus for crimping drawable filaments, comprising two nip rollers which apply pressure to the filaments and which are maintained at different temperatures and are thereby adapted to apply a modifying process across the crosssection of the filaments passing through the nip thereof, and drawing means for drawing the filaments so that the draw point or regionof necking is at or close to the The drawing means may operate upstream and/or downstream of the nip, and in this connection there may be driven forwarding rollersbefore the nip rollers, from which the nip rollers are adapted to draw the filaments by driving the nip rollers at a higher peripheral speed than the forwarding rollers, and further driven forwarding rollers adapted to draw the filaments away from the nip rollers by driving the further forwarding rollers to rotate athigher peripheral speeds than the nip rollers. The difference between the peripheral speeds of the forwarding rollers and the nip rollers may be equal tothe difference between the peripheral speeds of the nip rollers and the further forwarding rollers.

Adjustable guidesmay be provided which enable the filaments to enter the nip along the common tangent The drawing illustrates apparatus for crimping drawable filaments 10 comprising two nip rollers 11 and 12, adapted to apply a modifying process or processes differentially across the cross-section of filaments 10 passing through the nip thereof, and drawing means for drawing the filaments so that the drawpoint or region of necking is at or close to the nip.

The rollers 11 and 12 are differentially heated for the roller 11 to be a hot roller and the roller 12 to be a cooler roller. This may be done many known manner, but preferably both rollers are heated internally and their temperatures controlled. Alternatively the roller 11 can be heated, either by an internal electric heating element or by a radiant heater close to its outer surface, leaving the cooler roller 12 to reach an equilibrium temperature. It may be desirable toprevent the roller 12 from becoming too hot by cooling it, as by a small air jet, so that a significant temperature differential exists between the hot roller 11 and the cooler roller 12.

The drawing shows the filaments 10 being fed to the nip rollers 11 and 12 from a spinnerette 13 via guide rollers 14, 15, to driven forwarding rollers 16. A guide 17 between the forwarding rollers 16 and. the nip rollers is adjustable, as indicated by the chain line 18, to enable the filaments to enter the nip of the rollers 1-1 and 12 along the common tangent to the rollers, or to have a short are of .pre-wrap upon either of the nip rollers in advance of the nip.

Further driven forwarding rollers 19 draw the filaments 10 from the nip rollers 11 and 12, via another guide 20 which is adjustable, as indicated by the chain line 21, to enable the filaments to leave the nip rollers 11 and 12 along the common tangent to the two rollers, or to have a short are of post wrap, beyond the nip, upon either of the nip rollers.

From the draw rollers 19 the filaments pass to a windup 22, passing if desired through an optional oven 23 in which they can be annealed. Optionally, also, cooling means for the filaments can be provided downstream of the nip rollers 11 and 12, as indicated at 24, and may be a water bath or an air quencher.

The apparatus shown in the drawings can be operated in several different modes to produce crimped filaments, but the first process to be described has been found to cause the highest crimp levels to appear.

The filaments 10 pass from the forwarding rollers 16 to the nip rollers 11 and 12 along the common tangent to the nip rollers, and the latter are driven to rotate at a greater peripheral speed than that of the forwarding rollers 16, so that the yarn is drawn by drawing means operating upstream of the nip of the rollers 11 and 12, the draw point or region of necking being at or close to the nip. The filaments 10 are drawn from the nip of the nip rollers 11 and 12, along the common tangent to the nip roller, by the further forwarding rollers 19 the peripheral speed of which is greater than the peripheral speed of the nip rollers, so that the yarn is also drawn by drawing means operating downstream of the nip, the draw point or region of necking again being at or close to the nip. The difference between the peripheral speeds'of the forwarding rollers 16 and the nip rollers 1 l, 12 is equal to the difference between the peripheral speeds of the nip rollers and the further drawing rollers 19, so that the total draw imparted to the filaments is effected in substantially equal proportions by the drawing means operatingboth upstream and downstream of the nip. The total draw imparted to the filaments in this way preferably is equal to the maximum natural draw achievable having regard to the material of which the filaments aremade. Nip pressure is important to correct' processing and should be adjustable so that the filamentsare subjected to a predetermined pressure at the nip of the rollers 11 and 12, the precise pressure being dependent upon the material of the filaments and/or filament deniers. A nip pressure of about 4 pounds is suitable for crimping X filaments of 3 denier each. In operating the process the nip pressure is increased from a low value, while running filaments through the nip, until crimp appears and the pressure is then held at this value for maximum crimp. Further increase in pressure reduces the crimping effect and could flatten the filaments unduly.

b With a filament input speed of 30 metres per minute during experimental work, polyamides and polypropylene crimp well with a hot nip roller temperature which causes the filaments to experience l28-160C (preferably .145C) and a cooler nip roller temperature which causes the filaments to experience 9095C, polyesters with a hotnip roller temperature which causes the filaments to -experience l25,l40C (preferably 135C) and a cooler nip roller temperature which causes the :filarnents to experience 8085C. The overall preferred temperature ranges which the filaments experience are between..l25C and 160C for the hot roller and between 70C7and 110C for the cooler roller, depending upon the material of the filaments and the processing speed. Roller temperatures should be increased somewhat, within the specified ranges, as process speed is increased up to a speed at which theifilaments pass through the nip at aboutv 100 metres per minute. The temperature: differential which the filaments experience at the nip is thought to be an important parameter rather than the precise temperatures of either the hot orthe cooler nip'rollerss There are other modes of operating the apparatus shown in the-drawing to produce filaments having a useful degree of crimpQFor example all the required draw may be effected by driving the further feed rollers 19 to rotate at a faster peripheral'speed than the nip rollers Hand 12; or-it is possible that'the draw maybe incomplete'at this stage, and the'total required draw completed by further draw rollers (not shown) interposed between the further feed rollers 19 and the windup 22. v

The guide 17 can be adjusted to enable a short are of pre-wrap of the filaments to be applied to either of the nip'rollers 11 and 12, but preferably to the hotter roller 12, so that the filaments are pre-heated before running into the nip. The guide can be adjusted to enable a short are of post-wrap of the filaments 10 to be applied toeither of the nip rollers 11 and 12, but preferably to the hotter roller 12. The amount of prewrap or post wrap can be up to 30 degrees of arc, and

'pre-wrap orpost-wrap on the hot roller reduces the crimp level impartedto the filaments and thus can be used to control the crimp level.

In a further altemative a minor proportion of the total draw is effected by, the drawingmeans operating upstream of the nip, i.e., by driving the nip rollers 11, and 12 to rotate at a faster peripheral speed than that of the forwarding rollers 16.

' Depending upon the mode of operation employed to process the filaments, the nip rollers 11 and 12 can eiis preferred, or one roller can be driven and the other rotated by contact with the driven roller which is preferably the hot roller 12 since the filaments will tend to adhere more to this roller and be positively advanced. If the nip rollers are of sufficiently low inertia and the drawing means operates only downstream of the nip, the nip rollers could be driven by the yarn passing between them and one or other or both of the rollers could then be braked, as by a magnetic hysteresis brake, in order to control the drawing tension.

The crimped filaments pass from the further drawing rollers 19 to the wind-up 22, as has already been described earlier,vand in the zone between the rollers 19 and the wind-up 22 it has been proposed to provide an oven 23 for annealing the crimped filaments. The process can be carried out upon packages of undrawn or partially drawn filaments, as well as filaments taken directly from a spinnerette, and the end product is a continuous filament crimped yarn having a reversing helical crimp, and of high extensibility from a fully relaxed condition. In the zone between the roller 19 and the wind-up'22, the extensibility of the crimped yarn could be reduced by passing it through an annealing oven 23 under conditions of controlled overfeed of the yarn, a suitable percentage overfeed being between 10 percent and 40 percent according to the degree of reduction of extensibility which is required. The desired degree of overfeed could be obtained by an appropriate speed differential between the peripheral speeds of the rollers 19 and the wind-up 22, but a preferred arrangement would be to provide another pair of auxiliary yarn feed rollers (not shown) between the oven 23 and the windup 22 and to provide an appropriate speed differential between the rollers 19 and the auxiliary yarn feed rollers. This provides for the control of yarn tension between the auxiliary yarn feed rollers and the take-up 22, as is desirable for the winding of yarn packages.

Profiled nip rollers can be used, having spaced shallow circumferential grooves which receive the filaments while still providing that the filaments are nipped by the rollers, and this avoids the tendency of unprofiled'rollers to distort the filaments.

The process hasthe advantages that a wide range of textured effects can be imparted to continuous filament yarns because the process is controllable. Especially, close tension control of the filaments being processed can be maintained so that breakages are avoided or very much reduced. The temperature of the hot nip roller can be high enough for the production of novel yarns in which the filaments become welded together during processing but can be separated afterwards by stressing. The pressure which the nip rollers exert on the filaments can be adjusted to produce shiny or dull ya n- 7 Although the operation of the process is not fully un derstood, it is believed that the process changes the molecular orientation at one side of the filaments more than the molecular orientation at the other side, as the filaments pass through and are drawn at or near the nip of the nip rollers. Crimp formation appears to stem' as they experience the temperatures of the two rollers at the nip.

What is claimed is:

1. Method of crimping drawable filaments, comprising the steps of advancing a drawable filament through the nip between two rollers which are heated to different temperatures; subjecting said filament to a predetermined pressure during passage through said nip; differentially heating said filament during passage through said nip so as to establish a temperature gradient across the cross-section of the filament; and drawing the thus treated filament in such a manner that the draw point is at least close to said nip.

2. Method according to claim 1 wherein the drawing is effected by drawing means operating upstream of the nip.

3. Method according to claim 1 wherein the drawing is effected by drawing means operating downstream of the nip.

4. Method according to claim 3, wherein the filament is passed from the drawing means operating downstream of the nip to a wind-up, through a zone in which the filament is annealed while passing through said zone under conditions of controlled overfeed.

5. Method according to claim 4, wherein the percentage rate of overfeed is between percent and 40 percent.

6. Method according to claim 1, wherein the drawing is effected by drawing means operating upstream of the nip and by drawing means operating downstream of the nip.

7. Method according to claim 1, wherein the filament enters and leaves the nip tangentially to the rollers.

8. Method according to claim 1, wherein the filament approaching the nip are laid upon the hotter roller with a short is of prewrap in advance of the nip.

9. Method according to claim 1, wherein the filament arc of post-wrap after the nip.

leaving the nip is laid upon the hotter roller with a short 10. Method of crimping drawable filaments, comprising the steps of applying a modifying process differentially across the cross-section of the filaments while passing them through the pressure applying nip of two rollers of which one is a hot roller and the other is a cooler roller; and drawing the filaments in such a manner that the draw point is at or close to the nip, the total draw imparted to the filaments being effected in substantially equal proportions by drawing means operating both upstream and downstream of the nip.

1]. Method according to claim 10, wherein the filaments enter and leave the nip tangentially to the rollers.

12. Method according to claim 10, wherein the total draw imparted to the filaments is equal to the maximum natural draw achievable. I

13. Method according to claim 10, wherein the pressure applied to the filaments by the nip of the rollers is adjustable.

14. Method of crimping drawable polyester filaments, comprising the steps of advancing a drawable polyester filament in a path leading through the nip between two rollers one of which is heated to between substantially and C and theother of which is heated to between substantially l25 and C; laying.

close to said nip. 

1. Method of crimping drawable filaments, comprising the steps of advancing a drawable filament through the nip between two rollers which are heated to different temperatures; subjecting said filament to a predetermined pressure during passage through said nip; differentially heating said filament during passage through said nip so as to establish a temperature gradient across the cross-section of the filament; and drawing the thus treated filament in such a manner that the draw point is at least close to said nip.
 2. Method according to claim 1 wherein the drawing is effected by drawing means operating upstream of the nip.
 3. Method according to claim 1 wherein the drawing is effected by drawing means operating downstream of the nip.
 4. Method accOrding to claim 3, wherein the filament is passed from the drawing means operating downstream of the nip to a wind-up, through a zone in which the filament is annealed while passing through said zone under conditions of controlled overfeed.
 5. Method according to claim 4, wherein the percentage rate of overfeed is between 10 percent and 40 percent.
 6. Method according to claim 1, wherein the drawing is effected by drawing means operating upstream of the nip and by drawing means operating downstream of the nip.
 7. Method according to claim 1, wherein the filament enters and leaves the nip tangentially to the rollers.
 8. Method according to claim 1, wherein the filament approaching the nip are laid upon the hotter roller with a short is of prewrap in advance of the nip.
 9. Method according to claim 1, wherein the filament leaving the nip is laid upon the hotter roller with a short arc of post-wrap after the nip.
 10. Method of crimping drawable filaments, comprising the steps of applying a modifying process differentially across the cross-section of the filaments while passing them through the pressure applying nip of two rollers of which one is a hot roller and the other is a cooler roller; and drawing the filaments in such a manner that the draw point is at or close to the nip, the total draw imparted to the filaments being effected in substantially equal proportions by drawing means operating both upstream and downstream of the nip.
 11. Method according to claim 10, wherein the filaments enter and leave the nip tangentially to the rollers.
 12. Method according to claim 10, wherein the total draw imparted to the filaments is equal to the maximum natural draw achievable.
 13. Method according to claim 10, wherein the pressure applied to the filaments by the nip of the rollers is adjustable.
 14. Method of crimping drawable polyester filaments, comprising the steps of advancing a drawable polyester filament in a path leading through the nip between two rollers one of which is heated to between substantially 80* and 85*C and the other of which is heated to between substantially 125* and 140*C; laying the advancing filament with a short arc of pre-wrap upon said one roller upstream of said nip; subjecting said filament in said nip to a predetermined pressure and to a transverse temperature gradient; and drawing said filament by drawing means located downstream of the nip in such a manner that the draw point is at least close to said nip. 